CHICAGO — CT scans of 137 mummies spanning four geographies and 4,000 years of history show that hardening of the arteries was commonplace, especially in older individuals, suggesting this key sign of heart disease may be a part of aging rather than the byproduct of eating too many Big Macs.

The findings, presented on Sunday at the American College of Cardiology meeting in San Francisco and published in the Lancet medical journal, challenge the commonly held belief that atherosclerosis, or hardening of the arteries — the disease that causes heart attacks and strokes — is a modern plague brought on by smoking, obesity and sedentary lifestyles.

“It looks to be the case that this is an ancient condition of human population before the modern world and may in fact have been part of our species’ aging,” said Caleb Finch, a professor of gerontology at the University of Southern California and a senior author of the study.

The mummies included individuals from the prehistoric cultures of ancient Peru, Native Americans living along the Colorado River, the Unangan peoples of the Aleutian Islands between Alaska and Siberia, and individuals living in ancient Egypt.

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Overall, the team found signs of probable or definite atherosclerosis in 34 percent of the mummies studied.

“For mummies over age 40, half of them had some vascular calcifications,” said Dr. Randall Thompson of Saint Luke’s Mid America Heart Institute in Kansas City, who led the study.

“Considering we couldn’t see all of the arteries in any mummy, that is a reasonably high prevalence,” he said.

The findings are not the first evidence from mummies that atherosclerosis occurred in ancient peoples. Prior studies have shown evidence of hardened arteries in Egyptian mummies, but many believe that was due to the fact that ancient Egyptians only mummified elite members of society, who may have eaten a high-fat diet and gotten too little exercise, much like individuals in modern societies.

The latest study, however, spans a much broader swath of society, looking at individuals from different regions and societies and with very different diets.

“What we’ve put together in this is four cultures with very disparate lifestyles and geography. We have a more-convincing argument about the presence of this disease in ancient people,” Thompson said.

Finch said until the 20th century, infection was one of the biggest threats to human health. But advances in antibiotics and hygiene have expanded life spans long enough to expose the next big killer: age-related heart disease.

Heart disease is the leading cause of death in the United States for both men and women, killing about 600,000 people each year, according to the U.S. Centers for Disease Control and Prevention.

Finch said drugs that lower cholesterol, reduce blood pressure and thin the blood have been “a tremendous success story in 20th and 21st century medicine,” allowing millions of people to survive heart disease and live longer lives.

Even so, about one third of heart attacks arise in people who have no risk factors for heart disease except for their advancing age, he said.

“The question is, what can we possibly do to slow down the underlying basic process of atherosclerosis and aging in our blood vessels,” he said. “That, right now, is a blank wall.”